The default theme changed from Adwaita to Default and this tripped up
the logic to detect if the tarball builds contain pre-built css files or
not. Fix this by looking at pre-compiled css files in themes/Default/
instead of themes/Adwaita/.
theme_deps = []
# For git checkouts, but not for tarballs...
-if not fs.exists('theme/Adwaita/Adwaita.css')
+if not fs.exists('theme/Default/Default-light.css')
# ... build the theme files
sassc = find_program('sassc', required: false)
if not sassc.found()